Friday, March 4, 2011

Overeating and growth hormone release: a bad mix

One known effect of having too much body fat is a suppression of growth hormone release. The probable cause of this blunting of GH in the obese is that those who are too fat often have high levels of circulating free fatty acids in their blood. The relatively high concentration of free fatty acids blunts GH release. Another reason why those who are too fat may have blunted GH release is that they eat too much. Of course, eating an excess amount of food, combined with a lower physical activity is the most common cause of obesity. But according to a new study, eating an excessive amount of daily calories can also blunt GH release in those of normal weight. The study was designed to examine changes in GH secretion after three and thirteen days of overeating. None of the subjects were obese, and they were young with an average age of 24. This is important because GH release begins to drop off in most people at about age 40. All of the subjects remained in a hospital ward so that they could be closely monitored for the 13-day course of the study. They consumed meals that totaled 3,800 calories a day, definitely overeating for someone of normal weight, especially when not engaged in any type of exercise. Their 24-hour GH levels were measured at the start of the study, and after 13 days of overeating.

By the third day of the study, the average 24-hour GH level had dropped a whopping 70% in the over eaters. The decline in GH was  caused by a reduction in both the frequency and the amplitude of GH release. GH is normally released in pulses, with the highest level normally occurring after the first 90 minutes of sleep. This decline in GH release occurred despite the fact that none of the subjects had yet gained any additional weight from their voluntary gluttony. After 13 days of such eating, they had gained weight, but the effect on GH didn’t change.

One reason why many supplements touted as “GH releasers” don’t work is that they are not taken correctly. As noted above, maximal release of GH occurs under low blood glucose and low energy conditions. In practical terms, if you ingest a GH supplement (which usually contains amino acids, such as arginine and ornithine) in proximity to a meal, such as within 2 hours, the high level of glucose, fatty acids, and amino acids will prevent the release of GH, no matter how much of any supplement you ingest. For maximum benefit, you need to ingest these supplements on a completely empty stomach. Even then, the supplements may not work for various other reasons too complex to discuss here. For some, however, they will promote an increased GH response under the right conditions, as shown by several studies. In the meantime, be aware that overeating will effectively block GH release.

Cornford AS, et al. Growth hormone markedly suppressed after only a few  days of overeating.Appl Physiol Nutr Metab 2009;34:1124

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